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Feline Infectious Peritonitis in Cats

Feline Infectious Peritonitis (FIP) is a fatal
condition in cats where the causative virus (a coronavirus) which is
harmlessly present in most cats, mutates and becomes harmful. This mutation
is uncommon, but if it is present in one cat in a group, it will almost
certainly spread, as the affected animal sheds the virus in faeces very
freely and it will then spread as animals groom and socialise.

How Common is FIP?

Coronavirus is very common in cats and the incidence
increases with groups of cats of five or more. It is only possible to
estimate how widespread it is and ‘guestimates’ vary between 25% and 40% in
domestic cats in one or two cat households. In larger groups of household
cats or in catteries and rescue centres, this number is more likely to be
80%. Of these affected cats, some will shed the virus for a short time only
and then stop never to do so again. Others will shed it continuously. This
sounds a very worrying total, but this is the estimate for the harmless
version of the virus – the mutation rate is actually very low. Where FIP
becomes a threat is after the mutation has happened; a cat in which this has
happened can then infect the whole population and then it is very serious.

Why does the Virus Mutate?

The reasons for the mutation of the virus are not known
precisely, but it has been suggested that stress plays a large part in it.
Most mutations happen in younger cats and it is at this time of their lives
that most cats are most stressed; they are taken from their mothers and
home, they are vaccinated, they are introduced to other cats that may not be
friendly, they are spayed or neutered. Sometimes these events can quite
literally happen in the space of a few days and if the cat is already
infected with coronavirus, then this is the time when the virus will mutate,
when the cat’s defences against such a thing are down.

Pedigree Cats

Pedigree cats are more at risk than cross breeds and
also work is progressing on identifying certain genetic lines which seem to
be more susceptible to others, but this may turn out to be of purely
statistical interest as numbers affected remain relatively low. With all of
that said, some older cats in non-stressful situations also experience the
mutation of the virus into FIP, so these factors are not the only ones.
Viruses can mutate for no reason – the flu virus is a good example with
which we are all familiar.

What are the Signs of FIP?

The signs are very vague but quite severe and so your
immediate reaction will be to take your cat to the vet. It will be very
lethargic, with difficulty breathing due to the build-up of fluid in the
abdomen. It may have lesions on the eyes and have a wobbly walk or some
quite extreme behaviours, showing that the animal is hallucinating.
Diagnosis is quite difficult as there is no definite blood test for FIP, but
by using a combination of visual signs and various other blood tests such as
proteins and bilirubin (these are usually high) and a test for the
coronavirus antibodies can make the diagnosis more secure.

Is there any Treatment?

Sadly, there is no proven treatment for Feline
Infectious Peritonitis. Some vets give anti-inflammatory drugs and appetite
stimulants to improve the cat’s quality of life, and there have been a few
unproved examples of anti-virals making a difference to life expectancy, but
in practice the kindest thing if your cat has been definitely diagnosed with
FIP is euthanasia, always a difficult choice but in this case wholly
justified as the cat will be feeling very ill indeed and will not improve
until death intervenes.

Can FIP be Prevented?

As such, FIP cannot be prevented – there is a vaccine
but it has not been passed for use and most vets do not use it as unproven.
The best way of preventing FIP in your cat is to make sure that any new cat
you introduce into your home is from a small, stable community. FIP is
actually quite rare in household pets where the number of animals is less
than five. It spreads and mutates much more quickly in large communities
such as breeding catteries and rescue centres. In a household situation
keeping stress factors – such as worming, rehoming, spaying or neutering
when the cat is otherwise unwell – to a minimum should make sure that your
pet or pets remain unaffected by the mutated virus. This is the only
preventative measure you can take but it is remarkably effective.

Catteries

In catteries, it is inevitable that a large number of
the cats will have coronavirus, increasing the risk of mutating forms being
present. Keeping stress levels down and splitting large numbers of cats into
smaller stable groups can help minimise it. Checking a pregnant female for
coronavirus is also a good measure to take. If she is negative, it is vital
to remove her from the group and employ stringent hygiene measures to keep
her that way. Then she will not pass the virus on to her kittens and without
the initial viral contamination, FIP cannot follow. If she has coronavirus,
early weaning and removal of kittens can help – until four weeks of age,
they are protected by her antibodies.

How Worried should I be?

FIP is a nasty disease and fatal in almost every
correctly diagnosed case. It should be borne in mind, though, that its
incidence is about 1 in 5000 for households with one or two cats. With
around 19% of households owning a cat, this means that – without bothering
you will all the maths – in a town with around 50,000 people, you would have
one case of FIP. So the bottom line is, it is serious, but mercifully quite
rare.

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